The lipid composition of subcellular fractions isolated from rat and bovine glial cells will be determined. Evidence for a chain elongation system for the synthesis of very long chain (C greater than I8) fatty acids in glial cells will be investigated. Location of the enzyme system in the glial subcellular fractions will be established and conditions for optical activity of the system established. The activity of the chain elongation system in glial cells will be examined at different periods of brain development. The behavior of oligodendrocytes isolated in large quantities from bovine white matter will be studied in tissue culture.